American Osteopathic Association

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Microwaves and Plastics: How to Safely Re-Heat Your Leftovers

Woman using a microwavePlastics play a crucial role in our kitchens. From storing to serving, there are numerous ways our food comes in contact with plastic everyday. The question is: are all these interactions safe? When it comes to heating our food in microwaves, the answer is potentially, no.   

“When certain types of plastic are heated in the microwave, the substances and chemicals used in the manufacturing of the plastic can leak into your food,” explains Robert I. Danoff, DO, an osteopathic family physician in Philadelphia. “This plastic residual can raise health concerns when ingested, especially in infants and pregnant women,” he adds. 

However, that doesn’t mean that it’s unsafe to microwave all plastics.   

It depends on the type of plastic and on the type of food you are heating,” says Dr. Danoff. “Different plastics react to the microwave in different ways and fatty foods, in particular, like meats and cheeses, reach very high temperatures and may cause the plastic to warp or melt. This in turn has the potential to cause a chemical to seep out of the plastic and into the food.”

Is It Microwave-Safe?

That’s why it’s important to know what to look for when determining if certain plastics are safe for the microwave. 

“A good place to start is with the manufacturer's labels on your plastic containers,” says Dr. Danoff. 

Every plastic container intended for use with food has to undergo stringent testing performed by the FDA. If it is determined that a plastic product is safe for microwave use, then you will see either a microwave-safe symbol or written instructions indicating the product is microwave-safe. The number system found on plastics pertains to recycling and does not indicate whether or not the plastic is safe for heating. 

However, Dr. Danoff warns that not all microwave-safe products are safe to use in the microwave in the same way. 

“Though certain types of plastic wrap have received an FDA approved microwave-safe label, if it comes into direct contact with hot food (especially fatty foods) in the microwave, it may melt and release some of its contents into the food,” he says. “Therefore, you should leave at least one inch between plastic wrap and food before heating, or use alternatives like wax paper, parchment paper, or white paper towels.”

Microwave Dos and Don'ts

According to Dr. Danoff, there are certain types of plastics to always avoid when heating food in a microwave. These include: 

  • Restaurant takeout containers

  • Water bottles

  • Plastic tubs and jars made to hold margarine, cream cheese, yogurt, mayonnaise, mustard, etc.

  • Plastic storage bags or plastic bags from the grocery store  

Dr. Danoff also encourages people to follow these microwaving tips:

  • Never reheat the plastic tray formulated for frozen dinner and lunch entrees. These are intended for one-time use only.     

  • Vent the container when microwaving by leaving the lid ajar or lifting the edge. 

  • Ensure your product states “microwave safe” or contains instructions for use in the microwave.

“The important thing is to always read the labels of your plastic containers carefully before you put them in the microwave,” cautions Dr. Danoff. “If you are unsure, then it is best to heat your food in a microwave-safe container made of a different material, such as glass or ceramic.” 

 

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